Aerial propeller



- 1,628,716 May 1927' J. FISCHER AERIAL PROPELLER Filed mm 28, 1925 2Sheets-Sheet l J 1 25016 er May 17, 1927. 1,628,716

J. FISCHER AERIAL I ROPELLE IR Filed-A112. 28. 1925 2 Sheets-Sheet 2 rssPATENT OFFICE;

JOSEPH FISCHER, OI IlFAITH, SOUTH DAKOTA.

AERIAL PROPELLEB.

Application filed August 2a, 1925. Serial m. 53,155.

This invention relates to aerial propellers and has as its object toprovide a propeller which will be more eflicient in its aepropellers asordinarily tion that cavitation will be minimized in the openingsthereof, and air will be pocketed and banked behind the blades of thepropeller so that the blades will, in effect, .op-

' erate against a more or less compressed bank of air rather thanagainst rarefied air.

Another object of the invention is to so construct the blades of thepropeller that the portions thereof which constitute the means forbanking air behind the blades will tend likewise. to prevent distortionof 'the blades by continually reinforcing the so bld In the accompanyingdrawings:

Figure 1 is peller embodying the invention.

1Iiigure 2 is a front elevation of the prope er. I

Figure 3 is an end view of the propeller.

Figure 4 is a side elevaton of th propeller.

Figure 5 is a vertical sectional view taken substantially on the line5'5 of Figure 2, looking in the direction indicated by the arrows.

Figure 6 isa horizontal sectional view taken substantially on the line66 of Figure 2, looking in the direction indicated by the arrows. y

Figure 7 isa similar view taken substantially on the line 7-7 of Figure2, looking in the direction indicated by the arrows.

In the illustrated embodiment of the invention, the propeller comprisesa pair of counterpart blades indicated in general by the numeral 1, anda hub portion 2 to which pelled. Each of the blades the standard hub(not shown) may be fitted and the propeller thus mounted upon thepropeller shaft of the air craft to be pro- 1 comprisesa a perspectiveview of a pro-v body 3 which is of approximately ovate mar inal contourand is substantialy flat at its orward face, which is indicated by thenumeral 4, and has its'rear face slightly convex, as indicated by thenumeral 5, the body being relatively thin, as will be observed byrcference to Figures 5, 6 and 7 of the drawings. The leading edge of theblade is indicated by thenumeral 6 and the trailing or opposite edgeortion is indicated by the numeral 7. At its liist mentioned ed portion, the blade is formed to provide an aircompacting pocket indicatedby thenumeral 8. This pocket extends from the tip or outer end of theblade longitudinally of the trailing edge portion of the blade to thehubportion 2 and merges with the latter portion.

By reference to the several figures of the drawings, it will be observedthat the pockets 8 are located at the forwardfaces 4 of the blades andthat the walls of these packets are rounded transversely, the outer wall9 of each pocket being spaced from and opposing the said flat face 4 ofthe respective blade. Said wall 9 of the pocket is merged at its innerend with the surface of the hub portion 2, as indicated by the numeral10,

and the edge of the said wallis curved Ion-- gitudinally near the outerend of the pocket,

as indicated by the numeral 11, so that each pocket is of graduallydecreasing depth froma point inwardly of the tip of the respective bladeto the outer end of the pocket.

It will furthermore be observed by reference to the drawings, andparticularly Figure 2, thereof, that the material of the blades isgradually thickened along the bottoms of the pockets, in the directionof the hub portion 2, as indicated by the numeral 12, so that thepockets are of gradually decreasing depth in the direction of theirinner ends.

As the pockets are located at the trailing edge portions of theblades,their open sides are presented in the, direction of rotation of thepropeller audit will, therefore, be evident that as the propeller isrotated, air will be trapped in the pockets andcompacted so as toestablish, in eflect, a bank of air against-which the body 3 oftherespective blades may act. Therefore, cavitation is re IOI duced to aminimum and the air surrounding the revolving propeller is not sorarefied as where cavitatlon is'caused to a marked degree. Furthermore,there is less slip in the operation of the propeller embodying the invention than would be the case if the pockets were not present. Bgradually'deereasing the height of the wal s 9 of the pockets near theirouter ends, and forming the pockets of maximum depth at theirintermediate portions, the greatest cfiiciency is obtained H1 compactingthe air and, at the same time, the air trapped 1n the pockets may esca ewith minimum resistance, by way of t e outer ends of the pockets,through centrifugal force, in the rotation of the propeller;

It will be observed that the blades are oppositely diagonally disposed,as is the case in the ordinary propeller, and that the pockets of thetwo blades are substantially co-extensive as regards their outer walls9.

g It will be understood, of course, that while ing a wall confrontingthe forward face of the blade, the, said Wall, from a point near theouter end of the pocket being gradually decreased in depth in thedirection of the said end of the pocket.

2. An aerial propeller comprising rudiallr extending blades and anintermediate hub portion, each blade comprising a substantial- 1y flatbody of ovate marginal contour dis posed obliquely to the axis of thehub portion, and an air-compacting pocket extending along the trailingedge portion of in blade body.

3. An aerial propeller comprising oppositely extending blades and anintermediate hub portion, each blade comprising a sub stantially flatbody disposed obliquely to th axis of the hub portion, and anair-compacting pocket extending along the trailing edgr portion of theblade body, said pocket be ing transversely concave in cross section andhaving a wall confronting the forward surface of the blade body, saidwall merging at its inner end into the hub portion and the material ofthe blade being gradually thickened toward the hub portion wherein thepocket gradually decreases in depth to ward its inner end.

In testimony whereoi I ailix my signature JOSEPH FISCHER. [1,. 5.1

